Many of these concerns have now passed as a result of the Government's efforts to stabilise the sector, but many savers are still curious about the overall stability of their bank or building society. For comment on the stability of the industry in general, read our bank strength guide, while our bank safety guide outlines how you should spread your savings.

Santander Abbey - the background

Since Banco Santander bought Abbey in 2004, it has gone from strength to strength.

This was demonstrated by a 9% jump in profits to £9.9bn for 2008 while most other banks saw income plunge. This was put, in part, down to an influx of customers seeking safety in size; over the first nine months of 2008, the bank saw a net inflow of savings of £4.3bn, which was 70% up on the same period the year before. That additional flow of captial enables Santander to be bolder than rivals in lending it out and making a profit.

During the boom years, Abbey resisted borrowing on wholesale markets (the mistake of HBOS, B&B and Northern Rock) relying instead on funding from savings deposits. But it entirely avoid the excesses of that period, launching a 125% mortgage in September 2007.

Parent bank Santander's overall stability is exemplified by its eagerness to acquire other banks around the world, including the UK's Alliance & Leicester and Bradford & Bingley's savings book in late 2008.

Fitch revised the bank's outlook following its announcement on 14 October last year that it will acquire the remaining 75.65% of Sovereign Bancorp Inc, a holding company whose primary subsidiary is the US savings bank Sovereign Bank.

Santander's rating remains unchanged; the ratings agency merely wanted to find out whether the bank is overstretching itself with its spate of recent acquisitions.

Abbey was one of the eight institutions to originally sign up to the Government's £25bn offer of liquidity to the banking industry in late 2008, but has decided not to avail of the offer.

The acquisition of Bradford & Bingley's savings book has acted as a short-term drain on its finances, but it may not affect the long-term profitability of the business and may in fact substantially add to it.

Key events

• Santander was deemed one of the Top 10 strongest banks in the world in a survey of the world's best 1,000 banks by The Banker magazine, with profits of £9.5bn in 2008/09. It was the third most profitable bank after two Chinese banks.

• In May 2009, the company announced that it would ditch the Abbey, B&B and A&L brands in the UK and put everything under the Santander banner.

• On 5 February 2009, Abbey said statutory profits grew by more than 20% to £991m in 2008. It captured almost 30% of the new mortgage market in the UK last year, almost treble its level in 2007.

• The Spanish owner of Abbey announced on 14 December 2008, that its potential exposure to the Bernard Madoff $50bn fraud may be as high as over £2bn.

This is the highest potential loss of any bank with interests in Britain (Santander owns Abbey and the savings arm of Bradford & Bingley) and could easily wipe out profits made over the past two years.

• On 13 October, Santander announced plans to strengten the finances of its UK High Street financial services chains Abbey and Alliance & Leicester with a £1bn cash injection: Santander's £1bn cash injection